Analytical Sciences

Photocontrollable Cation Extraction with Crowned Oligo(spirobenzopyran)s

Makoto NAKAMURA, Hidefumi SAKAMOTO, and Keiichi KIMURA

Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, Sakae-dani 930, Wakayama 640-8510, Japan

The photoinduced changes of metal-ion extractability of crown ether derivatives bearing three or four spirobenzopyran moieties and their analogues were studied using 1,2-dichloroethane as the organic solvent. Under dark conditions, these compounds extracted Cu²⁺, Ag⁺, and Pb²⁺ with their counteranions from the aqueous phase to the organic phase. The extraction equilibrium constants of the photochromic crown ether derivatives for Cu²⁺ and Ag⁺ were determined successfully. Under UV-light irradiation conditions, the extraction of Cu²⁺ by crowned tris(spirobenzopyran) was enhanced, while that of Ag⁺ was suppressed. During the competitive metal-ion extraction of crowned oligo(spirobenzopyran)s between Cu²⁺ and Ag⁺, the metal-ion selectivity was reversed explicitly by photoirradiation.

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